Sealing the Subfloor and Ceiling Penetrations

by Paul LaGrange

Air Sealing of Penetrations in Subfloor and Ceiling

All holes and penetrations in the top plates, ceiling and subfloor should be sealed with expandable foam or caulking to prevent air infiltration into the conditioned space of the building. Holes are often cut or drilled for piping or wiring and can be found by following pipes and wires to their entry point into the ceiling or floor.

Unsealed penetrations allow unconditioned, humid air to flow into the walls. Wall cavity insulation does not inhibit air flow because insulation is not an air barrier – it is only effective when it is sealed between airtight materials. After all holes and penetrations are sealed, they should be re-covered with appropriate insulation. Insulation should be cut to fit neatly around obstructions or wiring – crushing or compacting insulation makes it useless.

Examples of attic penetrations are recess can lights, ceiling fans, chandeliers, pipes, wires, and air conditioning vents. Examples of subfloor penetrations are pipes and wire.

The photos below show examples of common penetrations (not properly sealed). The illustration below shows how to seal penetrations with caulk.